Viral Upper Respiratory Infections (Colds and Influenza) and Zinc Supplements

Zinc supplements may be useful in preventing and treating colds and, to some extent, the flu. Research evidence indicates that zinc supplements support the immune system, which is particularly helpful during cold and flu season. The immune system does not function properly if you don't have enough zinc in your body.^1-2 Because zinc is commonly deficient in the diet, especially among children and senior citizens,³ nutritional zinc supplementation may certainly be useful for those who get sick easily.

Zinc lozenges and nasal sprays and gels are also potentially effective options for treating a cold. (When you take zinc as a lozenge or nasal gel or spray, you are not using it as a nutrient. Instead, certain forms of zinc release ions that are thought to directly inhibit viruses in the nose and throat.)

Taking zinc in oral supplement form supports the immune system, which can then be more effective in combating the virus causing your cold or flu, or preventing illness altogether.

More topical forms of zinc, such as lozenges and nasal gels, work differently. They have a more direct antiviral effect on the viruses that cause colds.

Read more details about Zinc Supplements.

A 1-year, double-blind study of 50 nursing home residents found that zinc supplements as compared to placebo reduced rates of infection.¹⁵⁹ In addition, more than ten other studies performed in developing countries have found that zinc supplements at nutritional doses can increase resistance to respiratory and other infection in children, and that they might reduce symptom severity.^5-6,157,165

Zinc products--supplements, lozenges, and nasal gels and sprays--are widely available in drugstores and health food stores.

Based on a significant amount of research on zinc and colds, supplemental zinc and zinc lozenges have the most favorable evidence and the fewest potential side effects. Though zinc nasal gel has also demonstrated impressive results for treating colds, it can cause pain and possibly loss of sense of smell.

With supplemental zinc, more isn't better; once you do have enough zinc, getting extra won't help, and might even hurt (see Side Effects and Warnings).

Safety Issues

Zinc taken orally seldom causes any immediate side effects other than occasional stomach upset, usually when it's taken on an empty stomach. Some forms do have an unpleasant metallic taste. Use of zinc nasal gel, however, has been associated with anosmia (loss of sense of smell). ¹ In fact, After receiving over 130 reports of anosmia, the FDA warned consumers and healthcare providers in 2009 to discontinue use of certain Zicam Cold Remedy intranasal zinc-containing products, including Zicam Cold Remedy Nasal Gel, Cold Remedy Nasal Swabs and Cold Remedy Swabs in kids size. ² Furthermore, if the gel is inhaled too deeply, severe pain may occur.

Long-term use of oral zinc at dosages of 100 mg or more daily can cause a number of toxic effects, including severe copper deficiency, impaired immunity, heart problems, and anemia. ^{3 4 5} Zinc at a dose of more than 50 mg daily might reduce levels of HDL ("good") cholesterol. ⁶ In addition, very weak evidence hints that use of zinc supplements might increase risk of prostate cancer in men. ⁷ The US government has issued recommendations regarding "tolerable upper intake levels" (ULs) for zinc. The UL can be thought of as the highest daily intake over a prolonged time known to pose no risks to most members of a healthy population. The ULs for zinc are as follows: ⁸

• Infants

• 0-6 months: 4 mg

• 7-12 months: 5 mg

• Children

• 1-3 years: 7 mg

• 4-8 years: 12 mg

• 9-13 years: 23 mg

• Males and Females

• 14-18 years: 34 mg

• 19 years and older: 40 mg

• Pregnant Women and Nursing Women

• 18 years or younger: 34 mg

• 19 years and older: 40 mg

There are also some interactions between zinc and certain medications to consider:

Use of zinc can interfere with the absorption of the drug penicillamine and also antibiotics in the tetracycline or fluoroquinolone (Cipro, Floxin) families. ^{9 10 11 12 13} The potassium-sparing diuretic amiloride was found to significantly reduce zinc excretion from the body. ¹⁴ This means that if you take zinc supplements at the same time as amiloride, zinc accumulation could occur. This could lead to toxic side effects. However, the potassium-sparing diuretic triamterene does not seem to cause this problem. ¹⁵

Interactions You Should Know About

If you are taking:

• ACE inhibitors ; estrogen-replacement therapy ; oral contraceptives ; thiazide diuretics ; or medications that reduce stomach acid (such as H 2 blockers [ Zantac ] or proton pump inhibitors [ Prilosec ]): You may need to take extra zinc.

• Amiloride : This medication could reduce zinc excretion from the body, leading to zinc accumulation, which could cause toxic side effects. Do not take zinc supplements unless advised by a physician.

• Manganese ; calcium ; copper ; iron ; antacids ; soy ; or antibiotics in the fluoroquinolone (such as, Cipro , Floxin ) or tetracycline families: It may be advisable to separate your doses of zinc and these substances by at least 2 hours.

• Penicillamine : Zinc interferes with penicillamine's absorption so it may be advisable to take zinc and penicillamine at least 2 hours apart.

• Zinc supplements: You should also take extra copper and perhaps magnesium as well because zinc interferes with their absorption. Zinc interferes with iron absorption, too, but you shouldn't take iron supplements unless you know you are deficient.

1. Jafek BW, Linschoten MR, Murrow BW. Anosmia after intranasal zinc gluconate use. Am J Rhinol. 18(3):137-41.
2. FDA Public Health Advisory on Loss of Sense of Smell with Intranasal Cold Remedies Containing Zinc. Food and Drug Administration website. Available at: http://www.fda.gov/Drugs/DrugSafety/PublicHealthAdvisories/ucm166059.htm. Accessed: July 9, 2009.
3. Hoffman HN II, Phyliky RL, Fleming CR. Zinc-induced copper deficiency. Gastroenterology. 1988;94:508-512.
4. Sandstead HH. Requirements and toxicity of essential trace elements, illustrated by zinc and copper. Am J Clin Nutr. 61(3 Suppl):621S-624S.
5. Fosmire GJ. Zinc toxicity. Am J Clin Nutr. 51(2):225-7.
6. Hughes S, Samman S. The effect of zinc supplementation in humans on plasma lipids, antioxidant status and thrombogenesis. J Am Coll Nutr. 25(4):285-91.
7. Leitzmann MF, Stampfer MJ, Wu K, Colditz GA, Willett WC, Giovannucci EL. Zinc supplement use and risk of prostate cancer. J Natl Cancer Inst. 95(13):1004-7.
8. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001). National Academies Press website. Available at http://www.nap.edu. Accessed October 4, 2001.
9. Lim D, McKay M. Food-drug interactions. Drug Information Bulletin (UCLA Dept. of Pharmaceutical Services). 1995;15(2).
10. Drug Evaluations Annual. Milwaukee, WI: American Medical Association; 1993(2).
11. Neuvonen PJ. Interactions with the absorption of tetracyclines. Drugs. 11(1):45-54.
12. Mapp RK, McCarthy TJ. The effect of zinc sulphate and of bicitropeptide on tetracycline absorption. S Afr Med J. 50(45):1829-30.
13. Polk RE, Healy DP, Sahai J, Drwal L, Racht E. Effect of ferrous sulfate and multivitamins with zinc on absorption of ciprofloxacin in normal volunteers. Antimicrob Agents Chemother. 33(11):1841-4.
14. Reyes AJ, Olhaberry JV, Leary WP, Lockett CJ, van der Byl K. Urinary zinc excretion, diuretics, zinc deficiency and some side-effects of diuretics. S Afr Med J. 64(24):936-41.
15. Wester PO. Urinary zinc excretion during treatment with different diuretics. Acta Med Scand. 208(3):209-12.

1. Chandra RK. Trace element regulation of immunity and infection. J Am Coll Nutr. 1985;4:5-16.
2. Fraker PJ, Gershwin ME, Good RA, et al. Interrelationships between zinc and immune function. Fed Proc. 1986;45:1474-1479.
3. Werbach MR. Nutritional Influences on Illness. [CD-ROM]. Tarzana, CA: Third Line Press; 1998:630.
4. Girodon F, Lombard M, Galan P, et al. Effect of micronutrient supplementation on infection in institutionalized elderly subjects: a controlled trial. Ann Nutr Metab. 1997;41:98-107.
5. Bhutta ZA, Black RE, Brown KH, et al. Prevention of diarrhea and pneumonia by zinc supplementation in children in developing countries: Pooled analysis of randomized controlled trials. J Pediatr. 1999;135:689-697.
6. Sazawal S, Black RE, Jalla S, et al. Zinc supplementation reduces the incidence of acute lower respiratory infections in infants and preschool children: a double-blind, controlled trial. Pediatrics. 1998;102:1-5.
157. Kurugol Z, Akilli M, Bayram N, et al. The prophylactic and therapeutic effectiveness of zinc sulphate on common cold in children. Acta Paediatr. 2006;95:1175-1181.
159. Prasad AS, Beck FW, Bao B, et al. Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress. Am J Clin Nutr. 2007;85:837-844.
165. Kurugol Z, Bayram N, Atik T. Effect of zinc sulfate on common cold in children: Randomized, double blind study. Pediatr Int. 2007;49:842-847.